NEW YORK -- Right-hander Josh Johnson is scheduled to make his first rehab start for Class A Advanced Dunedin on Monday night.

Johnson has been out of action since April 21 because of soreness in his right triceps muscle. He was originally expected to return during the middle of May, but the discomfort lingered longer than first anticipated.

Toronto's No. 3 starter likely will be out another three weeks as he begins the slow process of building up arm strength and endurance in preparation for a return to the Major Leagues.

"If he comes out of that Monday [start] feeling good, that will be a good sign," manager John Gibbons said. "But I think it will be at least three [rehab starts].

"It's like Spring Training almost all over again. Not quite as bad."

Johnson is expected to pitch approximately three innings in his first start with Dunedin and will then increase his pitch count each time out. With the required four days of rest between outings, it's possible the process won't be completed until the second week of June.

That could also change if there are any setbacks, but as of now the Blue Jays are confident that the inflammation has been eliminated. Johnson would represent a welcome addition to a Toronto starting rotation that is already dealing with an injury to J.A. Happ and the seemingly lost Ricky Romero, who is currently struggling for Triple-A Buffalo.

The 29-year-old Johnson is 0-1 with a 6.86 ERA in four starts for the Blue Jays this season. He has struck out 19 and walked nine in his 19 2/3 innings of work.